Rising energy costs and the tightening up of legal provisions relating to permissible fuel consumption or permissible pollutant emissions from motor vehicles, in which internal combustion engines are disposed, mean that it is necessary to take steps on the one hand to reduce the fuel consumption of internal combustion engines and on the other hand to ensure that the pollutant emissions discharged by the motor vehicle are kept low. In this context it is known that internal combustion engines, in particular those operated using gasoline, can be operated at certain operating points using a self-igniting method, also referred to as a homogeneous charge compression ignition, compressed auto ignition or spatial ignition method. With this self-igniting combustion method, the automatic ignition and therefore the combustion pattern are controlled by way of the reactive energy quantity in the cylinder of the internal combustion engine. This energy quantity can for example be provided by means of a very high residual gas level compared with gasoline engine operation with conventional ignition. It is also known for gasoline engines with conventional ignition that the internal combustion engine can be operated with a high exhaust gas recirculation rate in the lower and middle partial load range, to optimize combustion in respect of the consumption and emissions quality criteria.
DE 199 007 38 C1 discloses a method for determining a combustion chamber pressure pattern in an internal combustion engine. With said method an estimated value of a cylinder pressure is estimated as a function of a previous measured value of the cylinder pressure, a cylinder volume assigned thereto and a cylinder volume assigned to the estimated value of the cylinder pressure and a polytropic exponent by means of the polytropic equation. The polytropic exponent is predefined as a function of a cooling water temperature.